Motorola HK8040 car kit mystery USB socket

I recently bought a motorola car kit for my V60i. While I was installing it,
I noticed that it has a USB socket, though this isn't mentioned in the
manual. What's it for?

I assume it's for a mobile connection to the Internet, in the same way as
the "data cables" that are available. If so, what software is required and
where can I get it from? Also, the connection between the brain and the
cradle uses a 9-pin D connector, just like a PC serial port. Is this a
coincidence, or can it usefully be connected to a computer?

Thanks for any help,

Pete